1. Field of the Invention
The field of the invention relates to high resolution ultrasound visualization systems, particularly such systems which have applications in the field of medicine.
2. Brief Description of the Prior Art
In recent years ultrasound technology has become a valuable tool to medicine. Both x-rays and ultrasound waves are useful for visualization of internal structure in patients, however ultrasound waves possess many advantages over x-rays. Ultrasound waves in the low dosages used for visualization are relatively innocuous to the health of the patient, whereas x-ray radiation presents an acknowledged risk of tissue damage. Also certain types of soft tissue can be better differentiated by ultrasound waves than with x-rays. Particularly, tumors can often be detected without difficulty by an ultrasound visualization system.
Most ultrasound visualization systems operate externally, with a transducer being placed on the surface of the patient, or in proximity to the patient in an acoustical coupling medium. The internal structure of a patient can be detected either by the detection of reflection echoes or by through-transmission technology.
Some ultrasound systems have been adapted to be used within the body. See U.S. Pat. No. 3,938,502 to Bom, U.S. Pat. No. 3,817,089 to Eggleton et al., and German Offenlagungsschrift No. 2,305,501. By these systems, transducers are placed on catheters and can thus be positioned within hollow organs in the body. In this manner the internal structure of various organs, such as blood vessels or the heart, can be viewed ultrasonically. Such systems typically operate at a frequency in the range of 5 MHz to 15 MHz.
Another ultrasonic aid in medicine is the acoustic microscope, in which high frequency ultrasound radiation is focused on a subject to produce high resolution magnification. See "Acoustic Imaging with Holograph and Lenses" by Glenn Wade, IEEE Transactions on Sonics and Ultrasonics, Vol. SU22, No. 6, November, 1975, which discloses one such acoustic microscope which operates at a frequency of 600 MHz. While perhaps not prior art, see also "The Acoustic Microscope" by Calvin F. Quate, Scientific American, Vol. 241, No. 4, October, 1979.
Ultrasound visualization systems have also been used to guide manual operations within the interior of the human body. U.S. Pat. No. 4,029,084 to Soldner and U.S. Pat. No. 3,556,079 to Omizo are two such patents which disclose ultrasound systems which are used as an aid in guiding the medical instrument into the body, such as a needle to be used for the puncturing of a blood vessel.